Electrochemical measurement and mass loss have been applied to acquire the corrosion rate, but the accuracy is limited when the corrosion is in its early stages. In this study, the early stages corrosion behavior of Q235 steel in 3.5% NaCl solution with pH=5 was investigated. The early stages corrosion kinetics behavior was obtained by traditional electrochemical approach, and the corrosion rate was calculated by Faraday’s law. Furthermore, the samples were carried out by conventional static immersion test. Subsequently, the volume reduction was measured by laser scanning confocal microscope (LSCM), the weight loss was also obtained. By comparing the corrosion rates obtained by these methods, it was obtained that corrosion rate in early stages obtained by volume reduction was the most accurate, which could be used to revise the corrosion rate obtained by other methods.